This is a guage. It has worked for me. I know when I need to get air. I think that's all it's supposed to do and that's all it does do. Works fine for me. They're a little expensive, but they came on my tank so it doesn't matter to me. They work good so if you need a guage you can get this one.
A nice guage. It works perfect and hasn't broken or anything yet. The only thing I don't like about it is the price i saw. It was really expensive at the store, but it came on my tank when I bought it for free so it didn't matter to me.